The present invention relates to liquid heaters for brewing beverage products, for reconstituting dried food products by supplying heated water thereto and for heating liquid food products. More specifically, the present invention relates to liquid heaters utilizing direct electrical resistance (DER) heating devices.
Conventional beverage makers such as coffee brewing machines have water storage tanks, commonly made of stainless steel, to hold water and heating rods with which to heat the water in the water storage tanks. The heating rods include tubes packed with sand and heat generating filaments. Heat generated by the filament is transferred to the sand and, then, to the water in the water tank, thereby heating the water.
Other conventional beverage makers include water boilers similar to the hot water storage tanks except that these boilers are held under pressure enabling the water to be heated to a higher temperature.
These conventional beverage makers, however, suffer from a number of drawbacks. For instance, they require a lengthy cold start period during which a cold water tank, or a boiler, filled with unheated water is heated. They also require a long recovery time when heated water is dispensed and, then, replenished with unheated water. In addition, the water quality tends to degrade over time when kept at a high temperature for prolonged periods of time.
In an effort to alleviate the above drawbacks, some of the conventional coffee brewing machines include on-demand water heating devices. These conventional on-demand water heating devices heat water only when requested. Conventional on-demand heating devices that produce small quantities of heated water include indirect electrical resistance heaters which are bonded to a water pipe. On the other hand, conventional on-demand heating devices that produce larger quantities of heated water include heating blocks which contain a coiled water tube and a coiled heating rod encased in a block of metal. The heating block is a thermal energy storage device to heat water on-demand as unheated water passes through the heating block. This requires a constant supply of electrical power to the heating block in order to maintain it at a certain temperature, thereby wasting electrical energy and losing thermal energy to its environment. In general, the conventional on-demand water heaters are inefficient, among other reasons, because they utilize the indirect resistance heating method.
In addition, due to the drawbacks described above, the conventional heating devices cannot produce heated water at a stable temperature which is a desirable feature in brewing some high quality beverages.
Instead of the conventional water heating method described above, direct electrical resistance (DER) heating methods have been developed for industrial uses. The DER method is also known as electroheating, in-line heating or ohmic heating. A conventional DER device includes a pair of electrodes and an electric power supplier for applying a high power to the electrodes. As an electrically conductive medium, such as meat or other food products, passes between the electrodes, electric currents flow through the medium which generate heat therein. The medium generates heat since it acts as a resistor.
Several references disclose the DER methods for heating different types of electrically conductive medium. For instance, U.K. Patent Application No. GB-A-2304263 (the xe2x80x9c""263 applicationxe2x80x9d) discloses an electroheating, processing, pasteurizing and cooking liquid egg. In this electroheating method, liquid egg is pasteurized when it passes through a pair of electrodes while electric power is applied between the electrodes. This method, however, heats only one type of electrically conductive medium, the liquid egg, in a controlled production line. In addition, this method, as with other conventional DER heating methods, requires a high power electrical power supplier among other industrial strength parts, which tend to be relatively expensive for nonindustrial use.
Accordingly, a general purpose liquid heater using a DER heating device is provided in the present invention, which does not have the drawbacks of the conventional DER heating devices described above.
First of all, the DER heating device of the present invention draws its electrical power from electrical power outlets commonly supplied to homes, offices, restaurants or food servicing facilities. The DER heating device of the present invention is also adaptable to varying electrical conductivity of different types of liquid. Further, electrodes of the DER heating device of the present invention are made of rigid, relatively insert, electrically conductive material tolerant of wear, e.g., graphite. Other advantages over the conventional water heaters are also described in detail below.
In addition, since the heating device of the present invention utilizes a DER heating device, it is capable of rapid and efficient transfer of the electrical energy into the water as thermal energy while reducing the energy loss associated with the indirect heating methods of the conventional beverage makers discussed above.
More specifically, the liquid heater of the present invention includes a first electrode having an electrically conducting surface and a second electrode having a first electrically conducting surface disposed spaced apart from the electrically conducting surface of the first electrode. The liquid heater also includes a first heating passage defined, at least in part, by the electrically conducting surfaces of the first and the second electrodes, the first heating passage including a first opening configured to receive liquid into the heating passage. Electrical power to the liquid heater is provided by an electrical power supplier configured to draw an alternating electrical current having a frequency lower than or substantially equal to 60 Hz and supply an alternating electrical voltage having a frequency substantially equal to or higher than 50 Hz across the first and second electrodes. In this configuration, the first and second electrodes are arranged to make electrical contacts with liquid received into the heating passage, and the liquid in the heating passage generates heat when an electric current flows between the first and second electrodes and through the liquid. It should also be noted that the alternating electrical voltage to be supplied across the electrodes can have a frequency between 20 KHz and 200 KHz.
Advantageously, the electrical power supplier may include an AC/DC converter configured to convert the alternating electrical current to a direct electrical current, a voltage level controller configured to adjust a voltage level of the converted direct electrical current, and a DC/AC converter configured to generate the alternating electrical voltage to be supplied across the electrodes based on the adjusted voltage level of the converted direct electrical current. The electrical power supplier can further include a transformer coupled to the electrodes and the DC/AC converter, the transformer configured to increase electrical power of the alternating electrical voltage to be supplied across the electrodes. If desired the voltage level controller can further include a pulse width modulated signal generator configured to produce a plurality of pulses each of which having a respective pulse width, a duty cycle switch configured to multiply the plurality of pulses with the direct electrical current from the AC/DC converter, and a filter to generate the adjusted voltage level of the converted direct electrical current. Also, if desired, the second electrode can have a pattern on its electrically conducting surface. The patterns can be a number of arcuate grooves.
In order to control the heated liquid production more efficiently, the liquid heater of the present invention can also include a temperature sensor configured to measure the temperature of the heated liquid, a current meter configured to measure the electrical current flowing between the electrodes and through the liquid, and a controller configured to generate a voltage adjustment signal based on at least one of the measured temperature and the measured electrical current. With this configuration, the voltage level controller is further configured to adjust the voltage level of the converted direct electrical current based on the voltage adjustment signal.
Further, other configurations of the electrodes can be provided. For instance, the first electrode can have a rod shape is disposed within the second electrode that has a cylindrical shape. If desired, additional electrodes that have cylindrical shapes and electrically conducting inner and outer surfaces can also be provided. In this configuration, the second electrode further includes an electrically conducting second surface, and additional heating passages are defined by the electrically conducting second surface of the second electrode and the inner surface of an inner most electrode among the additional electrodes and defined by electrically conducting inner and outer surfaces of the additional electrodes when the additional electrodes are disposed concentrically among each other and from the first and second electrodes.
In yet another configuration of electrodes, the first and second electrodes can have substantially flat surfaces. If desired, additional electrodes with substantially flat surfaces can also be provided. In this configuration, additional heating passages are formed by the additional electrodes when they are disposed in parallel and spaced apart from each other.
In the various electrode configurations described above with multiple heating passages, each heating passage is in liquid communication with adjacent heating passages in order to allow liquid heated in one heating passage to flow to its adjacent heating passage. Further, the electrical power supply is configured to supply electrical voltages to the additional electrodes in an alternating polarization configuration. In addition, the controller can be further configured to adjust the electrical voltage applied to each of the electrodes or to turn on or turn off the alternating electrical voltage applied each of the electrodes.
The present invention also provides beverage product dispensers for use in homes, offices, restaurants and food service facilities using any one of the DER heating devices described above to heat water to make beverage products such as espresso, coffee, hot chocolate, and tea. The beverage product dispenser of the present invention brews the beverage products under desired extraction condition, which may include the temperature of the heated water and the pressure under which the beverage products are brewed, in order to make consistently high quality beverage products. The DER heating device of the present invention can also be utilized in heating liquid food products such sauces and liquid cheese.
The beverage dispenser of the present invention may include a water pipe and a water source connector to supply water to a heating unit. The heating unit includes an inner and outer electrode forming a heating passage. The water supplied to the heating passage generates heat when an electric current flows through the water and between the electrodes. The heating unit is surrounded by an insulating tube and fluid sealed by an inlet sealant and an outlet sealant. The heated water is released to a dispensing head. The dispensing head releases the heated water to a brewing chamber in which the heated water is mixed with grounded beverage substance to produce beverage products.
The beverage dispenser also includes a controller which regulates the amount of water supplied to the heating unit and the amount of electrical current supplied to the electrodes to ensure that the heated water at the dispensing head reaches an optimal water temperature.
In addition, the present invention provides liquid food product dispensers for use in homes, offices, restaurants and food service facilities using DER devices to heat water to reconstitute dried food products or to mix hot water to concentrated food products.
In another embodiment, the present invention also includes a method of heating liquid which includes the steps of supplying unheated liquid into a heating passage formed between a first electrode and a second electrode, passing the liquid through the heating passage, and simultaneously applying an alternating electrical voltage between the first and second electrodes, to thereby generate heat within the liquid supplied to the heating passage when an electrical current flows through the liquid. The method further includes the steps of measuring the electrical current flowing through the liquid, and adjusting the alternating electrical voltage applied to the first and second electrodes based on the measured electrical current, to thereby efficiently control the heating rate of the heated liquid.
If desired the method can further include the steps of converting an alternating electrical current with a frequency lower than or substantially equal to 60 Hz to a direct electrical current, adjusting a voltage level of the converted direct electrical current, and generating the alternating electrical voltage to be supplied across the electrodes based on the adjusted voltage level of the converted direct electrical current. The step of adjusting the voltage level of the converted direct electrical current can also include the steps of generating a plurality of pulses each of which having a respective pulse width, multiplying the plurality of pulses with the direct electrical current, and generating the adjusted voltage level of the converted direct electrical current.
In order to efficiently control the heated liquid production, the method can further include the steps of terminating the electrical voltage applied to the first and second electrodes when the measured amount of the electrical current exceeds a predetermined amount, or calculating conductivity of the liquid supplied to the heating passage based on the measured electrical current. If desired the method can further include the steps of measuring temperature of the heated liquid, and adjusting the amount of the liquid supplied to heating passage based on the measured temperature.